Niacin, a B vitamin that's been a mainstay of heart treatment for years, provided no benefit in a major new study, and may even cause harm.

Niacin is commonly used to try to lower "bad" LDL cholesterol and raise "good" HDL cholesterol.

In a study of 25,000 people taking cholesterol-lowering statin drugs, doctors randomly assigned people to get either a placebo or niacin plus another drug to reduce flushing, a common side effect of niacin.

The niacin combination had no benefit, with no reduction in the rate of heart problems such as heart attacks, stroke or death.

But patients given niacin had a higher risk of bleeding, infections, new-onset diabetes or diabetic complications, according to a study presented today at a meeting of the American College of Cardiology in San Francisco.

"Finding out a drug is not helping people is just as important as finding that it has benefits — the net result is that people are healthier," said Jane Armitage, lead author of the study and a professor at the University of Oxford, in England, in a statement. Although doctors hoped niacin would prevent heart attacks and strokes, "We now know that its adverse side effects outweigh the benefits."

The study is the latest in a string of bad news for niacin.

A 2011 study found that it failed to reduce heart attacks, even though it boosted good cholesterol. Alarmingly, researchers found that users of niacin had a slightly higher risk of stroke, although this could have been a coincidence.

Niacin's poor performance in rigorously controlled trails is a disappointment, given that Americans spent $800 million a year on brand-name, extended-release niacin, said Robert Giugliano of Harvard Medical School in an editorial accompanying the 2011 study in The New England Journal of Medicine.

The negative results have caused doctors to move away from prescribing it.

To A. Marc Gillinov, a heart surgeon at the Cleveland Clinic, the new study is "another nail in the coffin for niacin."